The present invention relates generally to radiation detectors and devices. More specifically, the present invention relates to multi-layer radiation detectors and related methods, including methods of making radiation detectors and methods of performing radiation detection.
Scintillation spectrometers are widely used in detection and spectroscopy of energetic photons (e.g., X-rays and y-rays). Such detectors are commonly used, for example, in nuclear and particle physics research, medical imaging, diffraction, non destructive testing, nuclear treaty verification and safeguards, nuclear non-proliferation monitoring, and geological exploration.
A wide variety of scintillators are now available and new scintillator compositions are being developed. Among currently available scintillators, thallium-doped alkali halide scintillators have proven useful and practical in a variety of applications. One example includes thallium doped cesium iodide (CsI(Tl)), which is a highly desired material for a wide variety of medical and industrial applications due to its excellent detection properties, low cost, and easy availability. Having a high conversion efficiency, a rapid initial decay, an emission in the visible range, and cubic structure that allows fabrication into micro-columnar films (see, e.g., U.S. Pat. No. 5,171,996), CsI(Tl) has found use in radiological imaging applications. Furthermore, its high density, high atomic number, and transparency to its own light make CsI(Tl) a material of choice for x-ray and gamma ray spectroscopy, homeland security applications, and nuclear medicine applications such as intra-operative surgical probes and Single Photon Emission Computed Tomography or SPECT.
Scintillation spectrometry generally comprises a multi-step scheme. Specifically, scintillators work by converting energetic photons such as X-rays, gamma-rays, and the like, into a more easily detectable signal (e.g., visible light). Thus, incident energetic photons are stopped by the scintillator material of the device and, as a result, the scintillator produces light photons mostly in the visible light range that can be detected, e.g., by a suitably placed photodetector. Various possible scintillator detector configurations are known. In general, scintillator based detectors typically include a scintillator material optically coupled to a photodetector. In many instances, scintillator material is incorporated into a radiation detection device by first depositing the scintillator material on a suitable substrate. A suitable substrate can include a photodetector or a portion thereof, or a separate scintillator panel is fabricated by depositing scintillator on a passive substrate, which is then incorporated into a detection device. Fabrication of scintillator panels typically includes depositing scintillator material directly on a passive surface of a substrate, such as substrates made of glass, graphite, or having amorphous carbon as a major constituent.
Unfortunately, extensive processing of a substrate surface prior to direct scintillator deposition is often required since, for example, imperfections on the target surface may result in unacceptable performance or degradation of performance of the scintillator in a detection device. Such processing is time consuming and costly, and adds additional steps to detector manufacturing while often decreasing product yield. Additionally, different substrates can widely vary, for example, with respect to attributes such as physical characteristics (e.g., texture, hardness, permeability to moisture, and susceptibility to various forms of damage) and/or energy or light transmission properties. Thus, manufacturing processes separately tailored to each particular substrate may be required, further increasing detector manufacturing time and expense. Furthermore, suitability for direct deposition of certain scintillator materials may be limited only to certain substrate materials. For example, substrate surfaces coated with a reflective layer, such as silver, aluminum, and the like, and having a scintillator material such as CsI deposited thereon, may result in poor performance due, for example, to chemical corrosion or degradation, as the iodine in the scintillator can react with and tarnish the reflective coating.
Thus, a need exists for improved scintillator detector fabrication methods and radiation detectors that can make use of a variety of different substrates and scintillator compositions. In particular, new radiation detectors are needed that can be efficiently and economically produced and which can be fabricated using a variety of different substrates without the need for extensive processing or the need for individually tailored fabrication methodology, and which can make use of various scintillator and substrate combinations without loss of performance due, for example, to adverse chemical interactions or degradation of the detector performance.